Re: [cobalt-users] Raq3, bulk emailing and a lame DoS

["Nathaniel Scott" <cobalt@xxxxxxxxxxxxxxxxx>]

> I'm sending out a newsletter to about 4000 subscribers or so, using a PC
> based software called WorldMerge. I'm using the software (rather than
> majordomo) as I require "personalization" of the messages. Messages are
> sent out one by one. However, after about each 250-270 emails or so, the
> email server falls down and the Raq emails me (the admin) the error
> message:
>
> *****
> The SMTP (mail) server appears to be down.  The mail server may shut
itself
> down temporarily under extreme load, so you should also check the CPU load
> on the server...  blah, blah...
> ****
>
> I cannot mail more messages, neither from WorldMerge nor Outlook (socket
> errors: 10061 and 10022). The problem corrects itself after about 10
> minutes, but forces me start to from the beginning with a 'cropped'
> recipients-list. Very annoying.  Next time I'll write a script for this
> job, although that won't change much with regard to the load produced.
>
> I have difficulties believing that the server could be under 'extreme'
> load, as WoldMerge only sends out a message every 2-3 seconds or so (I'm
> working remotely via a dial-up). When I look at top, sendmail never has
> more than a few threads open using about 0.1% CPU each.
>
> Does anyone know why this DoS occurs and what can be done to prevent it?


Hmm. I don't know why it's crashing if you're doing separate messages and
not cc's.  Are these large files with graphics?

That's a pretty big mail list to tie up your server with.  My only
suggestion is to possibly bypass the Raq's sendmail and use a direct mailing
program like Advanced Direct Remailer: http://www.mailutilities.com/adr/.
Disclaimer:  I am not affiliated with these guys, nor have I tired their
product yet - I just bookmarked the site incase I ever had to do a large
mass mailing.

<snip from their site> ..."powerful remailer and mass mailer which send your
message straight out to the recipient's mail server (without your ISP's SMTP
server). ADR realizes multi-threaded direct delivery, and so works several
times quicker than usual email client.."

It's shareware, so there's not much to lose by trying it.

Just my $0.02

----------------------------------
Nathaniel Scott
The Cyber Image
http://www.thecyberimage.com